Investigators trying to determine what sparked the deadliest mass shooting in modern U.S. history have found the massacre to be the work of a sophisticated planner with the means and desire to inflict unprecedented carnage.

But on the second full day after Stephen Paddock smashed out the windows of a high-floor suite on the Las Vegas Strip and opened fire on a crowd of unsuspecting concertgoers, authorities still were trying to understand what drove him to such evil.

Several new details emerged Tuesday about Paddock — a 64-year-old retired accountant — and how he worked methodically to thwart law enforcement as he killed scores of people and injured hundreds more.

As he fired round after round during an 11-minute stretch from a suite on the 32nd floor of the Mandalay Bay Resort and Casino, Paddock used video cameras to keep an eye out for police storming his hotel room, according to Clark County Sheriff Joe Lombardo.

Paddock hid one camera in the peephole of his suite and two more in the hall, at least one of them disguised on a service cart, authorities said. At one point, he shot numerous rounds through the door, wounding a security guard. Paddock eventually put a gun in his own mouth and pulled the trigger as SWAT officers closed in. They found him with blood pooling behind his head and around the empty shell casings that littered the carpet, a handgun near his body.

“It was preplanned, extensively, and I’m pretty sure that he evaluated everything that he did in his actions, which is troublesome,” Lombardo said.

The sheriff said investigators were “making progress” on determining a motive, but complete answers remained elusive. There were precious few clues in Paddock’s background.

An investigator works in the room at the Mandalay Bay Resort and Casino on Tuesday, in Las Vegas. A gunman opened fire from the room, killing at least 58 people and injuring hundreds. (AP Photo/Marcio Jose Sanchez)

Neighbors in several states where Paddock owned homes in retirement communities describe him as surly, unfriendly and standoffish. Paddock was the son of a bank robber who was once on the FBI’s most-wanted list and who authorities described at the time as a “psychopath,” but Paddock’s brother said their father was not involved in their lives when they were children.

Relatives say the roots of Paddock’s loner lifestyle might have been planted on July 28, 1960. On that day, when Paddock was 7, a neighbor from across the street took him swimming. The neighbor told a local newspaper at the time that she knew authorities were coming for his father, and she wanted to spare the young boy from the trauma of seeing his father taken away. From that point on, Paddock’s family was never the same.

Until carrying out the massacre Sunday night, Paddock had no criminal history himself. Despite repeated claims by the Islamic State to the contrary, he also had no ties to international terror groups, authorities said. He had done some government work during his career, as a letter carrier for the Postal Service, an agent for the Internal Revenue Service and an auditor for the federal government’s Defense Contract Audit Agency in the late 1970s and 1980s. He was divorced twice and recently had been dating a woman from the Philippines who has Australian citizenship. He was known to gamble routinely and extensively.

Some public officials seemed to suggest Paddock’s mind was troubled, though there were no immediate indications that he had been diagnosed with a mental illness or was anything other than fully aware of what he was doing.

“A normal person would not cause this type of harm to innocent people,” said Rep. Ruben Kihuen (D-Nev.). “Clearly, there was something wrong with this man.”

People close to the investigation also said that in the weeks before the attack, Paddock transferred a large amount of money — close to $100,000 — to someone in the Philippines, possibly his girlfriend. The significance of that development was not immediately clear, though investigators said they were interested in probing Paddock’s finances and his avid interest in high-stakes gambling.

The girlfriend, Marilou Danley, returned to the United States from the Philippines Tuesday night and was met at Los Angeles International Airport by FBI agents, according to wire reports. Investigators considered her a “person of interest,” Lombardo said. Sen. Dean Heller (R-Nev.) said that police are eager to talk to her, as Paddock “doesn’t meet any profiles” and the “best lead is through this girlfriend.”

“They don’t know a lot about who the girlfriend is and why she left the country a week prior to the shooting,” said Heller, who has been briefed by authorities. “She is someone they need to have this discussion with to better understand the shooting and what his thought process was.”

Douglas and Sylvia Vick from Texas pray at a makeshift memorial on the Las Vegas Strip on Tuesday. (Mark Ralston/AFP/Getty Images)

At his home in Orlando, Eric Paddock, Stephen Paddock’s brother, said he doubts Danley had any prior knowledge of the incident and speculated that Stephen might have been trying to quietly ensure her financial stability. Stephen Paddock loved and doted on his girlfriend, whom he had met when she was a hostess at a casino, Eric Paddock said. The couple often gambled side by side.

“He manipulated her to be as far away from here and safe when he committed this,” Eric Paddock said. “The people he loved he took care of, and as he was descending into hell he took care of her.”

The shooting — which left 59 people dead and injured more than 500 others — reignited the debate on Capitol Hill and across the country about whether lawmakers should impose new restrictions on firearms. Clark County Coroner John Fudenberg on Tuesday evening clarified that Paddock was among the 59 slain in the incident; previously, authorities had said he wasn’t.

Undersheriff Kevin C. McMahill, speaking after Fudenberg, warned that the number of dead and injured could fluctuate as the investigation progresses.

“The answer that the coroner provided you is the most recent, relevant number that we have,” McMahill said.

Caution tape lines the doors of the gunman’s suite on the 32nd floor of the Mandalay Bay hotel. (Bild Exclusive/Polaris.)

Several Democrats used the massacre to push for new restrictions, and House Speaker Paul D. Ryan (R-Wis.) asserted Tuesday that Republican leaders have no plans to advance a bill, which passed a House committee last month, that would make it easier to buy gun silencers.

Leaving the White House to visit hurricane-ravaged Puerto Rico on Tuesday morning, President Trump said that “we’ll be talking about gun laws as time goes by.”

Paddock brought 23 guns to his Mandalay Bay suite, which overlooked the concert grounds on the southern end of the Strip. Included in that cache was an AR-15-type rifle with a high-capacity magazine and 12 “bump stocks,” a modification that would allow a gun to fire as if it were an automatic weapon. He also brought another AR-15-type rifle with a magnification scope commonly used for hunting and a bipod stand to help steady it, according to law enforcement officials and experts who reviewed images of the weapons posted online.

“For this individual to take it upon himself to create this chaos and harm is unspeakable,” Lombardo said.

The guns appeared to be but a piece of the arsenal Paddock had acquired during a period of years, at least some of it legally obtained from major retailers such as Cabela’s, national retailer of guns and outdoor gear, and Guns & Guitars, a store in Mesquite, Nev., according to people familiar with the case. ATF Special Agent in Charge Jill A. Snyder said Tuesday Paddock had purchased shotguns, handguns and rifles in Nevada, Utah, California and Texas.

At Paddock’s home in Mesquite, Nev., investigators recovered 19 more guns and an explosive, and in his car, they found ammonium nitrate, a chemical that can be used in bomb making. At another property in Reno, Nev., investigators recovered five more handguns, two shotguns and a “plethora” of ammunition, Lombardo said Tuesday.

Paddock probably secreted the weapons to his Mandalay Bay suite using more than 10 suitcases he brought with him. Lombardo said hotel housekeeping had been there since Paddock checked in on Sept. 28 and spotted nothing nefarious.

Lombardo said investigators had scoured Paddock’s suite, his car and the homes in Nevada, and they were examining surveillance and body camera video evidence and other electronic items they had seized in their searches. Separately, Lombardo said the department had opened an investigation into the unauthorized release of images that show the crime scene. Another sheriff’s official confirmed the authenticity of those images.

Police also continued documenting the crime scene and performing the grim task of identifying those slain, some of whom died blocks away from the concert as they tried to flee or seek help. As of late Tuesday afternoon, authorities had tentatively identified all of the victims.

Since the shooting, horrific stories have emerged of lives cut short, some taking bullets as they sought to protect their loved ones.

Bobby and Jenny Parks, a married couple from California who had been high school sweethearts, were swaying to a love song when a bullet struck her. He held her as she died.

After Cameron Robinson, a 27-year-old from Utah, was shot in the neck, his boyfriend, Robert Eardley, carried him to a vehicle. Robinson died before they made it to a hospital.

Two people who met at the festival — Kody Robertson and Michelle Vo — were watching the final act together when a bullet struck her chest. Robertson threw his body over hers to protect her. Later, they were separated; he tracked her down to a hospital and was told late Monday morning that she was dead.

Paddock’s weaponry would have allowed him to fire both rapidly and precisely at the crowd that was several hundred yards away and below him. The shots — fired from two windows of Mandalay Bay’s golden facade, which Paddock had smashed out — sent thousands of people scrambling for safety under Vegas’s neon glow. Police on Tuesday showed body camera footage of officers scrambling to determine where the shots came from as they yelled for people to leave the area.

“They’re shooting right at us, guys,” an officer can be heard saying. “Stay down! Stay down!”

Hospitals across the region continued to treat patients from the scene, many of them seriously injured. Sunrise Hospital and Medical Center says as of Tuesday night, 59 patients remain in the hospital and 31 of them are still in critical condition. University Medical Center said it had 64 patients from the attack, 12 of them critical.

Roads inside the Mandalay Bay Resort are closed for investigation on Tuesday in Las Vegas. (The Washington Post)

Matt ZapotoskyMatt Zapotosky covers the Justice Department for The Washington Post's national security team. He has previously worked covering the federal courthouse in Alexandria and local law enforcement in Prince George's County and Southern Maryland. Follow

Devlin BarrettDevlin Barrett writes about national security and law enforcement for The Washington Post. He has previously worked at the Wall Street Journal, the Associated Press and the New York Post, where he started as a copy boy. Follow

Mark BermanMark Berman covers national news for The Washington Post. He also anchors Post Nation, The Post's hub for news, analysis and the biggest stories happening across the country. He has been at The Post since 2007 and previously covered transportation and local news. Follow

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